Flash memory is a form of EEPROM (Electronically Erasable Programmable Read Only Memory) that allows multiple memory locations to be erased or written in one programming operation. Flash memory is a transistor technology and is generally classified into NOR flash and NAND flash. The names refer to the gate logic architecture of the memory cells. NOR flash memory has a longer erase and Write times than NAND flash memory, but NOR flash memory has a full address/data interface that allows random access to any location. NOR is suitable for storage of program code that needs to be infrequently updated, as in digital cameras and PDAs.
NAND flash memory has faster erase and write times (per bytes, depending on the access), higher density and lower cost per bit than NOR flash. However, its I/O interface allows only sequential access of data. NAND flash memory is popular with flash memory cards, USB flash drives for data storage and other mass memory devices. Among those flash memory card formats are MultiMediaCard (MMC), Secure Digital (SD), Memory Stick (MS) and xD Picture card.
Although NAND flash memory is faster to write as compared to other flash technologies such as NOR, improvement of the programming performance of NAND flash memory is still desirable. As density requirements in memories are increasing and content pre-programming starts to be more routine, programming performance becomes more critical from cost point of view. In the past, because of power consumption degradation, the power circuitry that is used to provide the programming or erasing voltage (up to 20V in NAND) is driven low after every block (page) access, as shown in FIG. 1. As shown in FIG. 1, the ready/busy signal (R/B) is in the low state after the setup in the I/O is ready. At the same time, the programming voltage Vprg is ramped up from “L” to “H”. Only after the Vprg is sufficiently ramped up does the actual cell programming begin. Thus, the total programming time is the sum of the actual cell programming time and the ramping up time. As such, the programming or erasing operation is not highly efficient. In production where a large amount of data is programmed to the card prior to putting it into a sales package, for example, it is advantageous and desirable to provide a method for improving the speed for programming the memory devices.